In the field of printing, the most common type printer has been the printer which impacts against record media that is caused to be moved past a printing line or line of printing. As is well-known, the impact printing operation depends upon the movement of impact members, such as print hammers or wires or the like, which are typically moved by means of an electromechanical drive system and which system enables precise control of the impact members.
In the field of dot matrix printers, it has been quite common to provide a print head which has included therein a plurality of print wire actuators or solenoids arranged or grouped in a manner to drive the respective print wires a very short, precise distance from a rest or non-printing position to an impact or printing position. The print wires are generally either secured to or engaged by the solenoid plunger or armature which is caused to be moved such precise distance when the solenoid coil is energized and wherein the plunger or armature normally operates against the action of a return spring.
It has also been quite common to provide an arrangement or grouping of such solenoids in a circular configuration to take advantage of reduced space available in the manner of locating the print wires in that specific area between the solenoids and the front tip of the print head adjacent the record media. In this respect, the actuating ends of the print wires are positioned in accordance with the circular arrangement and the operating or working ends of the print wires are closely spaced in vertically-aligned manner adjacent the record media. The availability of narrow or compact actuators permits a narrower or smaller print head to be used and thereby reduces the width of the printer because of the reduced clearance at the ends of the print line. The print head can also be made shorter because the narrow actuators can be placed in side-by-side manner closer to the record media for a given amount of wire curvature.
In the wire matrix printer which is utilized for receipt and journal printing operation, the print head structure may be a multiple element type and may be horizontally disposed with the wire elements aligned in a vertical line and supported on a print head carriage which is caused to be moved or driven in a horizontal direction for printing in line manner across the receipt or journal paper and wherein the drive elements or transducers may be positioned in a circular configuration with the respective wires leading to the front tip of the print head. In the wire matrix printer which is utilized for business forms or like record media printing operation, the print head may be oriented in a manner wherein the nose is pointed downward for printing on the form, slip or like media while the carriage and print head are moved above and across the form or media in the horizontal direction.
In the dot matrix printer which includes a print head of the circular configuration and multiple element type, there is a requirement for movement of generated heat away from the print head. These print heads operate at high speed and at large loading in a compact environment so that such generated heat is disposed of through means of a heat sink. The heat sink surrounds at least a portion of the print head to transfer the heat to and through the heat sink by conduction and convection.
Representative documentation in the field of dot matrix printer heads includes U.S. Pat. No. 4,134,695, issued to J. E. Randolph on Jan. 16, 1979, which discloses a carriage for positioning a print mechanism with facility for retracting the print mechanism.
U.S. Pat. No. 4,064,984, issued to T. H. Toeppen on Dec. 27, 1977, discloses a releasable device for fastening a print head and includes a manually-operated control lever which effects the opening and closing of a pair of locking levers by cam action in the form of journal bearings in the control lever.
U.S. Pat. No. 4,229,114, issued to A. C. Van Horne on Oct. 21, 1980, discloses a mechanism for mounting a print head to the shuttle of a printer and is designed to facilitate easy removal and replacement of the print head. The shuttle includes two slots for receiving molded bosses of the print head. The shuttle also has two locking members which are spring loaded to secure the parts.
U.S. Pat. No. 4,239,402, issued to F. Jung et al. on Dec. 16, 1980, discloses a wire matrix print head configured for detachable mounting on a complementary shaped support and held thereto by a spring device which urges the complementary surfaces in secure contact with one another.
U.S. Pat. No. 4,469,454, issued to G. J. Crean on Sept. 4, 1984, discloses a print wheel mounting arrangement for a print head and ribbon cartridge assembly that provides for tilting the assembly into a inoperative position with the ribbon cartridge in an extended tilted position for removal and replacement of the print wheel.
U.S. Pat. No. 4,473,312, issued to E. Forschner on Sept. 25, 1984, discloses a fastening mechanism for removably fastening a print head housing and a carriage. A locking member on the carriage effects rotational and axial movement relative thereto and has abutment surfaces cooperating with cam surfaces on the housing to latch the housing and the carriage by action of a spring.
U.S. Pat. No. 4,514,100, issued to R. E. La Spesa on Apr. 30, 1985, discloses apparatus for mounting a print head on a movable carriage and includes a projection on the carriage, an opening in the print head to receive the projection, a compression spring for maintaining the projection in the opening, and a movable cam surface in contact with the projection.
And, U.S. Pat. No. 4,708,502, issued to K. Murakami on Nov. 24, 1987, discloses a mounting mechanism for releasably mounting a print head to a carriage which includes a pair of pivotable levers located on opposite sides of the print head. A spring biases the levers in a predetermined direction and the levers are pivotable between a print head secured position and a print head released position.